Removing impurities from metallurgical solutions



umree STATES PATENT oFFi-cE REMOVING IMPURI-TIE-S FROM METAL- LUB'GICAL SOLUTIONS Edgar C. Pitzer, Baltimore, Md-., assignor to American smelting and Refining. Company, New. York, N. Y., av corporation of New Jersey No Drawing; Application May 2, 1932, Serial No. 608*,853

7 Claims. (011 23 -125).

This invention relates to the treatment of varioussolutions, arsenic is one of the most comacidsolutions commonly employed in metalmon and also one whose removal is expensive and lurgical operations and provides a method for difficult. This is true because the electrodepv treating suchsolutions whereby" the impurities osition of arsenic from acid is in itself a very contained therein are either greatly reduced. in inefficient process and, in addition, arsine, a very 50 amount orentirely eliminated, depending on the poisonous gas, is generated. On the other hand, particular impurities under consideration, the the removal of arsenic bydistillation is an oblength of thetime of treatment, the temperature jectionable and expensive process. at which the treatment is conducted, and the By my invention it is possible to economically 10 form and amount of theremoval agent introduced remove such impurities as arsenic, antimony, 55 into the solution, as well as various other factors. selenium, tellurium and iron from acid solutions It iswell known in the art of metallurgy that such as are commonly used in metallurgical opleaching solutions, electro-winning electrolytes, erations. I am also able, in the case of many and like solutionstend, with use, to become conelectrolytes or leaching solutions, to effect a taminated with impurities resulting in a deselective reaction which results in the removal 30.

creased efficiency" which in time necessitates disor reduction to workable limits of some impuricarding the solution if noprovision is made for ties without removing other metallic values conthe removal of the objectionable impurities or tained therein. My invention contemplates addtheir' elimination to workable-limits. ing compounds of titanium, preferably titanium For example, in the electrolytic refining of sulphate, in small amounts to the solution concopper, containing among other" impurities, artaming impurities; which results in the impurisenic; antimony, selenium, tellurium, and iron, a ties being precipitated therefrom. In practicing large percentage of the arsenic and smaller perthe-invention, I prefer to remove aportion of the c'entages of antimony, iron, selenium, and; telelectrolyte and: add thereto a calculated amount 25' l'urium; in the impure copper anodes enter the of titanium sulphate. The solution is then agielectrolyte. If these impurities are not confined tated and allowed to stand until precipitation is within certain maximum limits the cathodes bep e Wh ch is usually accomp Within come impure and the purpose of the electrolysis a few hours. The precipitate is then filtered off is defeated, simila dimoulties present the or decanted from the solution and the solution 30. selves in the practice of by-product leaching and returned Circuit Operation generally in the use of electro-winning electrolytes. For takes from three eight hours although I example; 11-, i mo in th case of l mhave obtained satisfactory results at room tem- Winning electrolytes for iron 5111191193585 t on perature it is preferable to practice the invention up and cause a serious loss in power efficiency. at Slightly higher mp t in Order to 5 This is generally attributed to iron sulphate more p p pl dissolving the cathodes and after. the iron con- To more thoroughly Illustrate-110W y nv tent has reached a certain definite limit the solution functions the following sp fi xampl f tion must be discarded unless suitable means m i v t n as practiced wi a pp r r finl s can b found for removing t impurities electrolyte is given. A portion of the electrolyte 40 Various practices have, heretofore, been inwas withdrawn from the tank house and upon D d'ul'ged; in to overcome the detrimental effects fihemflfa'l analysls Was found to 0011mm the off the impurities which build up in the solutions follflwlng I used in the various metallurgical processes. In many cases the practice is made of removing a g gravlty L265 30 "grams per liter 190 45 portion of the electrolyte or leaching solution Co er do 459 each. day, the quantity removed depending upon gg f"" the amount of the critical impurity or impurities Arsenic present in the material undergoing treatment. .f"""'':":::: 50 In some refineries an attempt is made to remove d 1 75 a Iron 0---- the impurities to workable limits and return the Chlorine ()3 solution to the process while in some cases no Selenium 305 attempt is made to do this and those portions Tenurium @002 which are periodically withdrawn from the proc- Bismuth 96 ess are discarded.

Of the various impurities which occur in the I then added titanium dioxide dissolved in con- 11o centrated sulphuric acid at the rate of 5 grams per liter of electrolyte having a temperature of approximately 135 F. The solution was agitated for nearly one hour and then allowed to stand.

for approximately three hours, at which time the solution analyzed as follows:

Specific gravity 1.265 H2SO4 grams per liter 205 Copper do 45.9 Nickel do 12.8 Arsenic do 2.52 Antimony Trace Iron do 1.20 Chlorine do .03 Selenium None Tellurium None Bismuth do .04

As shown from the above table the selenium and tellurium together with practically all of the antimony were precipitated. The iron and bismuth content was materially reduced and arsenic was eliminated to such proportions that the electrolyte was suitable for return to and reuse in the tank house.

The removal of antimony is significant because it normally tends to deposit on the cathode and although it is common practice to prevent this by the addition of chlorine, generally in the form of hydrochloric acid or salt, to the solution, its maximum permissible limit is relatively low and is ordinarily reached quickly even though additions of a chloride are used to overcome its detrimental effect.

It will be noted in the above example that no copper or nickel is removed from the solution. When desired, these elements may be readily decreased by well known methods such as removing the copper .by the use of an-insoluble anode and subsequently evaporating the electrolyte down to approximately 50 Baum whereby the nickel is precipitated.

While I prefer to withdraw and separately treat portions of the solution it is, of course, obvious that the titanium sulphate may be added to the electrolyte as an addition agent. However, in such case, the titanium compounds will be lost in the slimes. By recovering the titanium compounds and regenerating titanium sulphate for treatment of subsequent portions of the solution the cost of operation is reduced. This is a comparatively simple process as the arsenic is readily removed from the titanium with a solution of caustic soda or with a solution of sodium sulphide, after which the titanium dioxide may be redissolved in concentrated sulphuric acid for treatment of subsequent portions of the electrolyte.

While I prefer adding the titanium as heretofore described it is to be clearly understood that the inventionis not to be so limited. For example, it is possible to add the titanium in the chloride forms. Again, acid cake, containing approximately 30% titanium dioxide, is nearly soluble in hot water and obviously the'titanium may be added in this manner. I have also been able to obtain satisfactory results by putting the acid cake directly into thesolution or electrolyte being treated and in such cases I have found that temperatures approximating the boiling point give better results than lower temperatures.

As previously indicated it is desirable to agitate the solution being treated after the addition of the titanium in order to thoroughly mix the constituents. This may be accomplished in a variety of ways but I prefer to agitate with air as such treatment aids in oxidizing any iron present.

While certain novel features of the invention have been disclosed and are pointed out in the annexed claims, it will be understood that various omissions, substitutions and changes may be made by those skilled in the art without departing from the spirit of the invention.

What is claimed is:

1. The method of treating a copper electrolyte containing one or more elements of the group comprising arsenic, antimony, iron, selenium and tellurium, which comprises adding to said electrolyte quantities of titanium in such form as will precipitate members of the aforesaid group from said electrolyte.

a. In purifying copper refining electrolytes and leach solutions contaminated with arsenic the improvement which comprises treating such a. solution with appropriate quantities of a salt of titanium thereby precipitating arsenic from said solution.

3. The method of eliminating to within workable limits impurities incopper electrolytes and like solutions which comprises subjecting such solutions to the action of titanium dioxide dissolved in concentrated sulphuric acid whereby such impurities are precipitated.

. 4. In the removal of impurities, such as arsenic, antimony, iron, selenium, tellurium and the like, from acid solutions utilized in copper metallurgical processes, the improvement which comprises precipitating such elements from the solution bymeans of titanium sulphate.

5. The process for reducing to low limits im-. purities such as arsenic, antimony, selenium, tellurium andiron in copper refining electrolytes without removing copper ,and nickel contained thereinwhich comprises treating an electrolyte containing such elements with titanium sulphate at a temperature of about 135 F. for approximately four hours.

6. The process of purifying a copper refining electrolyte containing in addition to copper one or more members of the group comprising nickel, arsenic, antimony, iron, selenium and tellurium, which comprises adding to such electrolyte titanium in a form capable of precipitating any members of the aforesaid group except nickel, agitating the electrolyte, allowing the electrolyte to stand until precipitation reaches a desired point and separating the precipitate from the thus purified electrolyte.

7. The method of reducing the amount of such impurities as antimony, arsenic, iron, selenium and tellurium in a copper refining electrolyte which comprises withdrawing a portion of such solution, agitating same with air in the presence of a titanium salt thereby precipitating such impurities and thereafter returning the purified electrolyte to the system.

EDGAR C. PITZER. 

